the only think you'd regret it not spending as much time with your mom as possible. My dad was diagnosed in January 09, he passed January, 10. Don't regret for a minute the time I spent with him prior to and and during his last days. I was by his side when he passed, While I knew it was coming, he went from bad to worse practically overnight and I am forever thankful I had a few last days with him.
yes, you need t be with your mom as much as you can. you also need to take care of yourself, you are going to go through an incredible amount of stress and emotion and it can and will take its toll on you.